The present invention relates to cleaning heat exchangers and is particularly related to a method and apparatus for cleaning contaminants and particulates from the interior surfaces of the heat exchanger. The present invention finds particular application in conjunction with heat exchangers for x-ray tubes and will be described with particular respect thereto.
X-ray tubes require high voltage electrical connections to operate. In addition, considerable heat is produced during the generation of x-rays. To facilitate reliable high voltage connections and cooling, the x-ray tube is enclosed in a housing. The housing includes suitable high voltage connections for tube operation and defines a cavity to provide for circulation of a cooling fluid around the x-ray tube. The cooling fluid, for example dialla oil, is pumped into the housing through an input port, circulates around the x-ray tube removing heat, exits the housing and passes through a heat exchanger to cool the fluid.
Since the cooling fluid is circulated around high voltage components of the x-ray tube, contaminants and particles that are suspended in the fluid can result in arcing within the x-ray tube housing. Such arcing has a deleterious effect on the x-ray tube system. The contaminants and particles oftentimes are present as a consequence of the manufacturing process for the heat exchanger.
In an operating x-ray tube installed in an imaging system, if the cooling fluid is overheated during generation of x-rays, carbon deposits can develop within the fluid circuit and deposit on the interior surfaces within the cooling system, including the inner walls of the heat exchanger tubing. These deposits can later be dislodged from the heat exchanger and circulate around the high voltage components within the housing. These contaminants can also be the source of arcing. Heat exchangers removed from operating units in the field are often reconditioned and reused. Thus, it is important to remove particulates and contaminants from the interior surfaces of the heat exchanger that may accumulate during the operation of the system in the field.
In an effort to clean new and reconditioned heat exchangers, the heat exchangers are usually flushed with heated fluid at x-ray tube system operating pressure of approximately 5 pounds per square inch. Some other methods of cleaning heat exchangers, used in other commercial or industrial applications, are not suitable for use in the x-ray tube environment. For example, some heat exchangers are cleaned by steam, solvents, aqueous solutions or by forcing brushes through the interior of the cooling tubing. Each of these methods has at least some of the following disadvantages: (i) contamination by condensation within the heat exchanger, (ii) difficulty in disposal of hazardous chemicals and (iii) insufficient cleaning and (iv) damaging the interior cooling tube surfaces. For at least these reasons, methods used to clean heat exchangers for other applications are not suitable for use in conjunction with high voltage x-ray tube cooling systems.
The present invention is directed to a method and apparatus that satisfies the need to provide for cleaning x-ray tube heat exchangers which is compatible with the unique operating environment in which the heat exchanger and associated cooling fluid operate. A method in accordance with one embodiment of the present invention includes connecting the heat exchanger to a fluid supply and delivery system. Fluid flow is provided from the fluid supply through the interior of the heat exchanger in a first direction. The fluid flow is pulsed a predetermined number of times to suddenly change the fluid pressure within the heat exchanger. The fluid flow is then pulsed a plurality of times through the heat exchanger in a second direction.
In accordance with another aspect of the invention, an apparatus for cleaning the interior of a heat exchanger includes a source of fluid and a fluid delivery system in fluid communication with the source of fluid. The fluid delivery system is connectable to provide fluid through the interior of the heat exchanger. A pump moves the fluid through the fluid delivery system. A valve is operatively connected to the fluid delivery system to control fluid flow to the heat exchanger. A controller is controllably connected to the valve. The controller generates a control signal for suddenly varying the fluid flow through the heat exchanger over a predetermined period of time.
One advantage of the present invention is that the interior surfaces of the heat exchanger are more completely cleaned of particulate matter and contaminants.
The present invention provides the foregoing and other features hereinafter described and particularly pointed out in the claims. The following description and accompanying drawings set forth certain illustrative embodiments of the invention. It is to be appreciated that different embodiments of the invention may take form in various components and arrangements of components. These described embodiments being indicative of but a few of the various ways in which the principles of the invention may be employed. The drawings are only for the purpose of illustrating a preferred embodiment and are not to be construed as limiting the invention.